2003 Z71 Fuel Issue

[BrianEX]

2003 Tahoe 5.3 flex fuel
I was driving last week and the engine just stopped.
I had it towed home and determined I wasn't getting fuel up at the fuel rail. I don't have a pressure gauge, but pushed the button in with a screwdriver and only a drop of gas came out.
I assumed the fuel pump. Dropped the tank and took the old one out. I have breather line and filler tube taped close so not to contaminate or spill gas.
I put in a new pump and decided to hook up lines and test while still on ground in case of issues. Still wouldn't start, but had a trickle of fuel out of pressure test valve when I pushed it in. Will start if I squirt starting fluid in intake.
Unhooked fuel lines at pump and turned key on. No fuel coming out.
Exchanged the fuel pump relay with AC one as they are same part number. Check fuse and looks good.
Any thoughts? Right now I'm wondering if I got a faulty new fuel pump, but I know that isn't likely.
Any thoughts on anything else I should check?
Should I unplug the breather and fuel fill lines?
Thanks.

 

[tokuzumi]

The 03 and prior has a fuel filter on the inside of the driver's side frame rail, under the driver's door.

Also, I think there is a fuel pressure regulator at the base of the intake manifold on the driver's side.

If those all check out, there's a clog in the lines somewhere before the schrader valve.